1. Field of the Invention
This invention is directed to a vehicle body mount disposed between a vehicle body and frame to cushion or damp vibration characteristics transferred between the body and frame. More particularly, the invention is directed to an improved two stage rebound cushion used in a body mount.
2. Discussion of the Art
Vehicles are typically equipped with a body mount that serves to isolate the transmission of vibration energy and impact energy from the vehicle and suspension and frame through the vehicle body. The body mount is positioned between the vehicle body and frame and provides vibration damping characteristics or cushioning.
A rebound cushion is typically used in conjunction with the body mount to provide additional cushioning or vibration damping. Rebound cushions normally employ an elastomeric member that is received within a support structure that secures the rebound cushion to the body mount. As will be appreciated, the elastomeric member is formed from plastic, rubber, or composite materials that exhibit energy absorption or vibration damping characteristics.
For example, a simplified rebound cushion includes an annular elastomeric member engaged or retained at one end by a stamped metal plate and a fastener that extends centrally through the plate and elastomeric member. That is, the body mount is disposed between the vehicle body and the frame, while the rebound cushion is located on an opposite face of the frame.
Typically, the rebound cushion of a body mount assembly has conflicting requirements. In order to provide adequate isolation, the rebound cushion must be vertically xe2x80x9csoftxe2x80x9d so as not to add excessive cushioning rate in that direction. Still another requirement is for the rebound cushion to provide progressive rate buildup and thereby prevent excessive travel during rebound. The rebound cushion also must remain in contact with the vehicle frame through the entire dampening stroke to prevent xe2x80x9cslappingxe2x80x9d or xe2x80x9cpoppingxe2x80x9d that may be exhibited on vehicle rebound.
Known rebound cushion assemblies often address only one of the two extremes. That is, they are either xe2x80x9csoftxe2x80x9d to satisfy the vibration isolation requirements or are very stiff to satisfy the travel restriction requirement.
It has thus been deemed desirable to provide a rebound cushion that overcomes the disadvantages noted with prior arrangements in a simple, economical manner that can be easily implemented and can be incorporated into known body mount designs.
A rebound cushion for a body mount that provides a low cushioning rate for improved isolation and a second portion that provides rebound travel control and prevents any slapping or popping associated with the assembly. The exemplary embodiment preferably has a first portion in constant compression.
An exemplary embodiment of the two stage rebound cushion has two independent rings. A first or inner ring is elongated and provides for a low vertical system cushioning ring since it is in constant compression even at extended travels. A second or outer ring provides desired rebound travel control upon contact engagement with the vehicle frame.
In a preferred embodiment, the first and second ring portions are interconnected by a thin membrane or web that permits independent motion of the first and second ring portions and yet allows the first and second components to be formed as a single piece assembly.